Online gaming has become increasingly popular in recent years. Currently, the most common business model of online gaming is based on monthly subscription fees that game players pay to obtain credits, which allow them to start or continue a journey in the game's virtual world. Therefore, from the perspective of game operators, predicting how many players will join a game and how long they will stay in the game is important since these two factors dominate their revenue.

This paper represents a pilot study of the predictability of online gamers' subscription time. Specifically, we study the gameplay hours of online gamers and investigate whether strong patterns are embedded in their game hours. Our ultimate goal is to provide a prediction model of online gamers, which takes a player's game hours as the input and predicts whether the player will leave in the near future. Our study is based on real-life traces collected from World of Warcraft, a famous MMORPG (Massively Multiplayer Online Role-Playing Game). The traces contain the gameplay histories of 34,524 players during a two-year period. We believe that our study would be useful for building a prediction model of players' future game hours and unsubscription decisions; i.e., decisions not to renew subscriptions.